1. Field of the Invention
The present invention relates to a fluid displacement apparatus, and more particularly, to a suction port mechanism of a scroll type refrigerant compressor used in an automotive air conditioning system.
2. Description of the Prior Art
Suction port mechanisms for fluid displacement apparatuses are well known in the prior art. For example, FIG. 1 depicts a suction port mechanism used in a scroll type refrigerant compressor as described in U.S. Pat. No. 4,596,520 to Arata et al. A compressor section 2 and electric motor section 3 are encased in hermetic housing 1. Compressor section 2 includes a stationary scroll member 5 and an orbiting scroll member 6 which form closed compression chambers 9 therebetween. Stationary scroll member 5 has a disc-shaped end plate 5a and a wrap 5b extending from end plate 5a. Wrap 5b is shaped as an involute curve. A discharge port 10 and suction port 7 are respectively formed in the central and peripheral regions of end plate 5a. Orbiting scroll member 6 has a disc-shaped end plate 6a, wrap 6b formed on one side of end plate 6a and having a contour conforming with that of wrap 5b of stationary scroll member 5, and a boss 6c on the other side of end plate 6a. Boss 6c receives an eccentric shaft portion 14a of a rotary shaft 14. Eccentric shaft portion 14a causes an orbiting movement of orbiting scroll member 6. Rotary shaft 14 is rotatably supported by a bearing 11a provided on a central portion of frame 11. Stationary scroll member 5 is fixed to frame 1 by a plurality of bolts, not shown, while orbiting scroll member 6 is supported by frame 11 through an Oldham coupling mechanism 12. Orbiting scroll member 6, therefore, makes an orbiting movement with respect to stationary scroll member 5 without rotating about its own axis. Rotary shaft 14 is connected at its lower end to an electric motor 3. Discharge port 10 opens to a discharge chamber 1a which, in turn, communicates with a lower chamber 1b through a passage, not shown, and further leads to a discharge pipe 19 which penetrates the wall of the hermetic housing. Further, a back pressure chamber 20 is defined by the rear surface of orbiting scroll member 6 and frame 11. The intermediate pressure between the suction pressure (pressure of the low-pressure side) and the discharge pressure is applied to back pressure chamber 20 to counteract the axial force produced by the gas under compression in the compression chambers between both scroll members. The intermediate pressure is introduced into back pressure chamber 20 through a small aperture 21 formed in end plate 6a.
Suction pipe 17 extends through the wall of hermetic housing 1 and connects with the suction port 7 formed in stationary scroll member 5. Suction pipe 17 is forcibly inserted into suction port 7 to obtain an adequate seal between the peripheral surface of suction pipe 17 and the inner wall of suction port 7. Suction pipe 17 is then welded to hermetic housing 1.
Scroll member 5 must be assembled within hermetic housing 1 so that suction port 7 is aligned with the hole in hermetic housing 1. Suction pipe 17 may then be force fitted into hermetic housing 1. The requirement of aligning scroll member 5 with the hole in housing 1 is time consuming and complicates the assembly process.